JS-常用的数据结构之链表的实现

function LinkedList(){
    var Node = function(element){
        this.element = element;
        this.next = null;
    };
    
    var length = 0;
    var head = null
   
    this.append = function(element){
       // 创建一个节点
       var node = new Node(element);
       var current = null;
       
       if (head == null){
           head = node;
       }else{
           current = head;
           while(current.next){
               current = current.next;
           }
           //找到最后一项，将其next赋为node，建立连接
           current.next = node;
       }
       length++;
    } //向链表尾部添加一个新的项

    this.insert = function (position, element) {
        // 检查越界
        if(position >= 0 && position < length){
            var node = new Node(element);
            var current = head;
            var previous = null
            var index = 0
 
            if(position === 0){
                node.next = current;
                head = node;
            }else{
                // 1 从前往后遍历找到position
                while(index < position){
                   previous = current;
                   current = previous.next;
                   index++;
                }

                //通过改变指针，将node链接在previous和current之间
                previous.next = node;
                node.next = current;
               
                // 2 经验证1和2没有区别
                //while (index++ < position) {
                //    previous = current;
                //    current = current.next;
                //}
                //通过改变指针，将node链接在previous和current之间
                //node.next = current;
                //previous.next = node;
                return true;
            }
        }else{
            return false;
        }
    }; //向链表特定位置插入一个新的项

    this.removeAt = function (position) {
        if(position > -1 && position < length){
            var current = head;
            var previous = null;
            var index = 0;

            if (position == 0){
                head = current.next;
            }else{
                while(index < position){
                    previous = current;
                    current = current.next;
                    index++;
                }
                previous.next = current.next;
            }
            length--;
            return current.element;
        }else{
            return null;
        }
    }; //从链表特定位置移除一项
    this.remove = function (element) {
        var index = this.indexOf(element);
        this.removeAt(index);
    }; //从链表中移除一项
    this.indexOf = function (element) {
        var current = head;
        var index = 0;
        while(current){
            if (current.element === element){
                return index;
            }
            current = current.next;
            index++;
        }
        return -1; 
    }; //返回元素在链表中的索引，如果没有则返回-1
    this.isEmpty = function () {
        return length === 0;
    }; //判断链表是否为空
    this.size = function () {
        return length;
    }; //返回链表包含元素个数
    this.getHead = function () {
        return head;
    }; //返回链表第一个元素
    this.toString = function () {
        var current = head;
        var str = "";
        while(current){
            current = current.next;
            str += "," + current.element;
        }
        return str.slice(1);
    }; //只输出元素的值
    this.print = function () {
        console.log(this.toString());
    }; //打印元素的值
}